The present invention takes into account problems associated with grinding disks and such like in equipment such as wood hoggers. However, many such devices are being used to break down a variety of different materials including soft and hard rocks, recycled asphalt and roading, demolition masonry, and tires etc. The problems encountered when acting on these different materials are largely similar, though some of the problems may be more prevalent when acting on different types of material. For simplicity of description, problems associated with wood hoggers comminuting wood materials will be referred to for the main part, though the teachings are applicable to related applications, such as (for instance) described above.
Typical disks (and we shall also include drums by inference as these are essentially a disk of greater thickness) used in wood hoggers and the like are generally made up of separate components, rather than being a single unitary component. Typically the disk is made up of a central hub portion and a plurality of disk sections radially distributed about this hub. Each of these disk sections, which generally resemble a sector in appearance (apart from a removed inner portion corresponding to the position of the hub) are generally fixed directly to the hub itself. In a log hogger, teeth are generally provided on either or both of the planar surfaces of the disk, and its circumferential edge.
A problem often arises when sudden resistance to rotation of the disk is encountered. Such resistance often occurs locally (i.e. centralized on a single disk section) and often has the effect and consequences of an impact. The cause of such ‘impact’ is typically the entry of foreign materials such metal and rocks into the system rather than the substantially softer wood which is being processed. Such impacts place an exceptionally high strain on the bolts, generally positioned on the inner end of the segments and connecting them to the hub. This can, in exceptional circumstances, lead to catastrophic failure of those bolts with potentially disastrous results for the disk assembly and associated equipment.
Fortunately, in well maintained equipment this is not common, though frequent maintenance is generally required, and the system is nevertheless occasionally exposed to significant stresses from such sharp impacts.
As wood hoggers are more commonly being used for breaking harder materials, including rocks and demolition materials, the impact and forces acting on teeth and disk segments increase significantly. The likelihood of catastrophic failure is increased, and the need for regular preventative maintenance becomes even more pronounced. Hence, what represented a problem for disks acting on wood, becomes a major problem for disks acting on harder materials.
Another problem which is often prevalent in grinding disks is the misalignment of disk sections, generally contributed to by repeated impacts. Ideally the sections should be positioned and retained such that the outer arcuate edges form substantially a perfect circle. However, over time, and as a consequence of impact, the arcuate outer edges of the sections can become misaligned, with steps resulting between adjacent sections. In current designs there is no easy fine adjustment to allow for quick realignment of the disk sections, and fixing the problem may require machining of the connections with the hub.
It is an object of the present invention to consider these problems and to provide the public with a useful choice.
It is also an object of the present invention to provide a system for the construction or connection of the disk assembly which addresses the stresses placed on individual disk sections as a consequence of localized impact and forces resulting from use.
It is also an object of the present invention to be able to provide a method of assembling a disk assembly wherein such localized impact enforces can be at least partially absorbed by a readily replaceable and potentially expendable element.
Aspects of the present invention will be described by way of example only and with reference to the ensuing description.